The goal of this proposal is to investigate protein-ligand and protein-protein interactions in HIV-1 reverse transcriptase (RT). Being a key player in HIV infection, RT is the molecular target of the majority of AIDS drugs. Ligands studied will include five nonnucleoside reverse transcriptase inhbitiors (NNRTI) as well as normal substrates. RTs studied will include up to five drug resistance mutants in addition to wild type. The enzyme copies the single-stranded genomic RNA into a double-stranded DMAprovirus, which is subsequently integrated into the host chromosome by HIV integrase. RT has RNA- and DMA-dependent DMA polymerase and RNase H activities. The biologically active enzyme is a heterodimer of p66 and p51 subunits. The p51 subunit is derived from p66 subunit by HIV protease. The proposal applies biochemical and biophysical techniques, including powerful site-specific fluorescence techniques, to fundamental investigations of proposed inhibition mechanisms and protein conformations that may reveal new targets for antiviral therapy. This laboratory is presently one of few using solution biophysical techniques to study RT. Specifically, we propose to: 1. Characterize inhibitor binding to RT. 2. Determine inhibitor effects on individual steps in DMA polymerization. 3. Investigate inhibitor effects on conformation and dynamics of RT subunits and assembly.